MEDEA (Disposal Strategies for MEO Orbits)

Project Description:

This research project was funded by ESA’s General Studies Programme in the frame of the GreenOPS initiative (, with Deimos in Spain as prime contractor and the Institute of Aerospace Systems as project partner. Main goal in the frame of the project is to investigate the impact on the collision risk within navigation constellations when performing different types of end-of-life manoeuvres for the disposal of satellites. All major navigation constellation in the medium Earth orbit were considered, which are the American GPS, the Russian GLONASS, the European Galileo and the Chinese Beidou. These different disposal manoeuvers were then considered within extensive Monte-Carlo simulations of the long-term evolution of the space debris environment using ILR’s tool LUCA (Long Utility for Collision Analysis). The resulting populations were analysed in regards to their changes in the collision risks, especially within the four constellations. In more details, three types of mitigation manoeuvers were performed:

  • Business as usual/no disposal: In this scenario, for GPS and Galileo, mitigation manoeuvres as either currently performed or currently planned were considered in the simulations. These manoeuvers aim for a clear separation of the disposed object to the nominal constellation, but do not ensure a long-term stability of the orbit. For GLONASS and Beidou, no disposal was assumed, thus the satellites were left were they are.
  • Disposal to stable orbits: In this scenario, for all constellations, at end of life of every constellation object a disposal to a long-term stable orbit, clearly separated from the nominal constellation, was implemented. This ensures that over timeframe of several hundred years, the disposed satellites do not come in touch with any of the nominal constellations and therefore have no impact on the collision rates of within the nominal constellations.
  • Disposal to unstable orbits: In this scenario, constellation objects at end of mission were disposal to orbits in which resonances between the gravitational potentials of Sun, Moon and Earth lead to a long-term eccentricity build-up which lets the satellite re-enter after about 200 years. In this scenario, the disposed satellites at some point get in contact again with the nominal constellations; therefore they have an impact on their collision rates. The great advantage is though that after a certain amount of time, the satellites are removed from space and therefore no accumulation of old satellites takes place.

Publications in the frame of this project

Radtke J., Domínguez-González R., Sánchez-Ortiz N., Merz K., Impact of Eccentricity Build-Up and Graveyard Disposal Strategies on Meo Navigation Constellations, Presented at the 40th COSPAR Scientific Assembly (COSMOS2014), 1.-10. August 2014, Mosow, Russia, paper COSPAR PEDAS.1-0023-14

  1. Domínguez-González, N. Sánchez-Ortiz, F. Cacciatore, J. Radtke, S.Flegel, M. Möckel, K. Merz, Disposal Strategies Analysis for MEO orbits, Conference: IAC2013, Volume: IAC-13.A6.2.5